Giant viruses were first discovered a few years ago, and they stunned researchers; they were unlike anything else. Many genes they carried had no equivalents in any known organisms. Now researchers have learned more about one reason why that is; these giant viruses are also gene factories. They can create new genes with new functions. A team of researchers has reported their findings in Nature Communications.
Three members of the Pandoravirus family have been isolated in Marseille, France, Nouméa, New Caledonia, and Melbourne, Australia. Although these viruses have characteristics in common - they have functions and shapes that are similar - they don't share even half of their protein-coding genes. These intriguing viruses are as big as bacteria, which is gargantuan on a viral scale. The influenza A virus is around 13,500 bases, cold viruses are about 8,000 bases, while the pandoravirus genome can be 2.7 million base pairs long.
Like two other pandoraviruses that have been characterized, the new ones also have many orphan genes, meaning they are unlike any other known genes from any organisms. Because these genes are not shared between the giant viruses, it suggests they don’t come from a common ancestor.
Researchers at the Structural and Genomic Information Laboratory (CNRS/Aix-Marseille Université), worked with colleagues at the Large Scale Biology Laboratory (CEA/Inserm/Université Grenoble Alpes) and CEA-Genoscope; they used bioinformatics for their analysis. The team found that the orphan genes have characteristics that are similar to the areas of the pandoravirus genome that don’t code for protein.
The scientists suggested that when taken together, the massive size of the pandoravirus genome, the differences between those genomes, and the many orphan genes they carry, it seems likely that many of the genes carried by the viruses originate from those non-coding regions. Novel genes could theoretically arise spontaneously in different viruses, making those strains unique.
This work could show that viruses are architects of genes and gene function, which may help shed light on the origins of life.
The video above from Wellcome Genome Campus Courses and Conferences features a lecture on giant viruses by Jean-Michel Claverie of CNRS, one author of the report in Nature Communications about the pandoravirus.